The invention relates to electrically driven power tools, such as rotary drivers and, in particular, to ratcheting-type drivers.
It is known to provide an electrically driven screwdriver which is of the ratcheting type. Such a power tool is disclosed, for example, in U.S. Pat. No. 4,448,098, and includes a battery-powered, reversible, DC electric motor. The ratchet mechanism is controlled by a selector cap which also simultaneously actuates a single reversible direction control switch for reversing the motor direction simultaneously with reversing of the ratchet direction. This arrangement permits a fastener to be run down by the use of the electric motor and, when the torque increases, final tightening can be performed manually, the manual operation being facilitated by the ratchet mechanism. However, if the single direction-control switch fails, the motor cannot be operated.
U.S. Pat. No. 2,979,089 discloses a battery-powered portable electric screwdriver, with a reversible motor controlled by a control circuit which includes two direction-control switches. However, the switches are ganged, and both switches must be operated to change the motor direction. Thus, if either switch fails, the motor cannot be operated in either direction.